This invention relates to a serial interface and more particularly to a generic interface that is automatically configurable for operation with different physical interfaces in either a data terminal equipment (DTE) mode or a data circuit terminating equipment (DCE) mode.
There are 12 primary serial interfaces currently used in industry. These interfaces include Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) EIA/TIA-232, EIA/TIA-449, EIA/TIA-530, and EIA/TIA-530A. These interfaces are also well known in the industry under the former EIA prefix "RS-" as RS-232, RS-449, RS-530, and RS-530A. Additional interfaces include International Telecommunications Industry (ITU) X.21 and V.35.
Each interface standard defines electrical characteristics of the serial signals, the number of interface pins and how the pins are connected to the interface signals. Each serial interface operates either as a DTE or as a DCE. A terminal or computer is typically referred to as the DTE and a modem is typically referred to as the DCE. A signal that is an output on a DTE is the input to the DCE on the opposite end of the serial interface. The DCE is the clock master when communicating to the DTE.
Network Processing Nodes (NPNs), such as routers, modems and network servers, might use different serial interfaces. A different serial cable and different serial interface circuitry is required to connect together each different combination of serial interfaces on two NPNs. Since there are so many different serial interfaces, many different serial cables, connectors and interface circuits are needed. Selecting and installing the right cable is difficult since the operator often does not know the specific serial interface used on each NPN.
Instead of supporting multiple serial cables, a NPN could support one generic serial interface which would be a super set of all other serial interfaces. The generic interface would use a generic connector which would connect to a transition cable which would then connect to the specific interface.
Existing generic serial interfaces include a generic connector on a first end of a transition cable. A second end of the cable includes a connector that conforms to one of the serial interface standards. However, these generic interfaces use a large number of different signals and as a result require a large connector with a large number of pins. Therefore, the generic interface circuitry used for configuring the large number of signals on the generic interface to different serial interfaces is also complex. Moreover, some generic serial interface cables include resistors in the cable which add cost and lower reliability.
Accordingly, a need remains for a generic serial interface that uses fewer generic signals and, in turn, fewer connector pins and less complex interface circuitry.